1. Field of the Invention
The present invention relates to a method of backfilling pipeline trenches.
2. Description of the Prior Art
According to the most conventional method of backfilling a pipeline trench, the bottom of the trench is first filled with a layer of sand or other bedding material which is then compacted to form a bed for the pipe. The pipe is then laid on this bed after which an aggregate padding material is dumped into the trench along the opposite sides of the pipe. Tampers and vibrators are use to compact the padding about the pipe to secure the pipe in its final position. However, it is difficult to obtain effective compaction of the padding in a region along the bottom of the pipe adjacent to its centerline at the interface of the bedding and padding materials. Quite often air voids remain in this region or at best it is left with only loosely compacted material, thereby creating a flow path for water that may trickle or otherwise find its way into the trench. Where the pipeline is laid on a gradient, which is common, a sufficient flow in the indicated region occurs to eventually wash away the bedding material from beneath the pipe, causing it to settle and finally rupture. Depending on the pipeline's location and the material transported, the possibility of such rupture can present a serious risk of damage to the environment, wildlife and human populations, and substantial loss of the transported resource.
Accordingly, there is a need for an improved method of backfilling pipeline trenches to avoid the aforementioned problems and risks presented by conventional backfilling methods.